desktop: add sway/swayfx profile (dormant) with waybar, kanshi, cliphist

New profile_desktop_sway role gated by desktop_sessions_enabled, with
SwayFX effects, Waybar bar (1:1 with Polybar layout + pulseaudio),
swayidle + swaylock-effects for locking, swayosd for OSD, cliphist for
clipboard history and kanshi for multi-monitor profiles. Emptty gains
WAYLAND_SESSIONS_PATH + wayland-sessions dir. start-sway wrapper handles
session env (dbus-run-session, gpg-agent, turnstile env). Profile stays
dormant until a host opts in via desktop_sessions_enabled.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

dotfiles/desktop/.config/sway/scripts/lockscreen

@@ -0,0 +1,20 @@
+#!/bin/sh
+
+exec swaylock-effects \
+    --image "$HOME/.config/sway/wallpapers/wallpaper-161664.jpg" \
+    --scaling fill \
+    --clock \
+    --indicator \
+    --effect-blur 7x5 \
+    --fade-in 0.3 \
+    --ring-color 2f4058 \
+    --inside-color 1f1f28 \
+    --line-color 00000000 \
+    --separator-color 3a3a46 \
+    --key-hl-color 6daeea \
+    --bs-hl-color c7162b \
+    --ring-ver-color 4a90d9 \
+    --inside-ver-color 1f1f28 \
+    --ring-wrong-color c7162b \
+    --inside-wrong-color 1f1f28 \
+    --text-color d0d0d0